• Applied Biological Chemistry
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• v.46 no.4
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• pp.305-310
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• 2003

Hydrophobic core variant of ubiquitin appeared to have partially folded structure at pH around 2. The intrinsic tryptophan fluorescence emission maximum of this ubiquitin variant at pH 2 showed slight blue shift compare to that of unfolded state, suggesting that some residual tertiary structures remain in this solvent condition. At the same solvent condition, this ubiquitin variant binds with hydrophobic dye, 8-anilinonaphthalene-1-sulfonic acid(AMS), which is known to bind to exposed hydrophobic surface. Furthermore, far-UV circular dichroic spectrum of this ubiquitin variant in the diminished pH was remarkably different from the far-UV CD spectrum of the native state or unfolded state. Based on the molar ellipticity at 220 nm, this ubiquitin variant at pH 2 appeared to have significant amount of secondary structures. All these observations suggest that this ubiquitin variant in the diminished solvent pH has loosely folded hydrophobic core with some secondary structures, which are key features of molten globule conformation. Since molten globule has long been considered as a protein folding intermediate, it is considered that this hydrophobic core variant ubiquitin will serve as a valuable model to study protein folding process.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.28.1-28.1
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• 2010

Recent surveys have shown that many early-type galaxies have signatures of ongoing or recent star formation (RSF). These RSF galaxies show blue integrated UV-optical colours that set them aside in the NUV integrated colour-magnitude relation. Among them, NGC 4150 has been observed using the Wide Field Camera 3 (WFC3) on board the Hubble Space Telescope to inspect the galaxy with higher spatial resolution. In the WFC3 data, the galaxy reveals ubiquitous near-UV emission and remarkable dusty substructure. Our analysis shows this galaxy to lie in the near-UV green valley, and its pixel-by-pixel photometry exhibits a narrow range of UV-optical colours that are similar to those of nearby E+A (post-starburst) galaxies, and lie between those of M83 (an actively star-forming spiral) and the local quiescent early-type galaxy population. This work reaffirms our hypothesis that minor mergers play a significant role in the evolution of early-type galaxies at late epochs.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.11
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• pp.1020-1024
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• 2006

Europium$(Eu^{2+}\;or\;Eu^{3+})$-activated calcium aluminium silicate phosphors were synthesized for the first time and the structures and luminescence characteristics of these phosphors were investigated. The phosphors in this study emitted blue, green, and even red light depending on the starting milterials and annealing conditions for synthesis. In addition, the structure was also changed when the different starting materials were used. When $CaCO_3$ was used as a starting material, tetragonal $Ca_2Al_2SiO_7$ was formed. However, pure green light was emitted when the annealing was conducted in reduced atmosphere and red one was emitted by annealing in air. In the case of $CaSiO_3$ as a starting material, triclinic $CaAl_2Si_2O_8$ was formed and only pure blue emission was observed. Moreover, this blue phosphor exhibited higher intensity than that of commercial YAG:Ce phosphor, which showed the possibility of application on the phosphor for new light source such as a UV-LED.

• Journal of the Korean Ceramic Society
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• v.37 no.2
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• pp.134-139
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• 2000

The main objective of the present investigation is to show the feasibility of combinatorial chemistry by applying this method to phosphor syntehses. In this respect barium hexaaluminate phosphor was prepared by the split-pool combinatorial method, which enabled much more rapid search of optimum compositions of target phosphors than conventional synthetic methods. Barium hexaaluminate phosphors doped with Eu2+ exhibit blue emission while those co-doped with Mn2+ and Eu2+ exhibit green emission. Basically, the phosphor doped with 1.3 mole of Ba and 0.06~0.15 mole of Eu2+ exhibit the maximum value of emission intensity at 435${\mu}{\textrm}{m}$. Under the UV and VUV extitations, the barium hexaaluminate phosphor co-doped with Mn2+ and Eu2+ shows strong green emission.

• Journal of the Korean Ceramic Society
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• v.43 no.3 s.286
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• pp.169-172
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• 2006

We have synthesized a $Eu^{2+}-activated\;{(Sr,Ba)}_2SiO_4$ yellow phosphor and investigated the development of blue LEDs by combining the phosphor with a InGaN blue LED chip (${\lambda}_{em}$=405 nm). The InGaN-based ${(Sr,Ba)}_2SiO_{4}:Eu$ LED lamp shows two bands at 405 nm and 550 nm. The 405 nm emission band is due to a radiative recombination from a InGaN active layer. This 405 nm emission was used as an optical transition of the ${(Sr,Ba)}_2SiO_{4}:Eu$ phosphor. The 550 nm emission band is ascribed to a radiative recombination of $Eu^{2+}$ impurity ions in the ${(Sr,Ba)}_2SiO_4$ host matrix. In the preparation of UV Yellow LED Lamp with ${(Sr,Ba)}_2SiO_{4}:Eu$ yellow phosphor, the highest luminescence efficiency was obtained at the epoxy-to-yellow phosphor ratio of 1:0.45. At this ratio, the CIE chromaticity was x=0.4097 and y=0.5488.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1090-1092
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• 2006

There is provided white light illumination system including a radiation source, a first luminescent material having a peak emission wavelength of about 575 to about 620 nm, a second luminescent material having a peak emission wavelength of about 495 to about 550 nm, which is different from the first luminescent material and a third luminescent material having a peak emission wavelength of about 420 to about 480 nm, which is different from the first and second luminescent materials. The LED may be a UV LED and the luminescent materials may be a blend of three phosphors. A human observer perceives the combination of the blue, green and red phosphor emissions as white light.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.968-971
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• 2003

Due to a low efficiency of phosphor with large Stoke shift in Vacuum Ultra Violet (VUV) excitation environment, new PDP phosphors which can be excited in UV excitation environment need to be developed. In this study, $Zn_2SiO_4:Tb$ phosphor was synthesized by solid-state reaction method at $1300^{\circ}C$ with varying Tb concentration, and its cross relaxation effect was observed by Photoluminescence (PL) measurement. In order to decrease $^5D_3{\to}7F_j$ transition with blue emission in $Zn_2SiO_4:Tb$ phosphor, Dy, co-activator element, was added to $Zn_2SiO_4:Tb$ phosphor. In 254nm excitation environment, broad-emission peak was observed around 524nm, green emission.

• Journal of Biosystems Engineering
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• v.25 no.4
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• pp.287-292
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• 2000

The herbicide penetration on weed leaves was spatially analyzed by using chlorophyll fluorescent emission and machine vision technique. Velvetleaf and metribuzin were used as experimental materials in the study. The herbicide spray images were obtained by a combinaton of a fluorescent dye and a UV lighting system. The herbicide penetration was analyzed by means of detecting chlorophyll fluorescent emission under blue-green lighting. According to the experiment results, the number and the size of spray droplets decreased with coverage increasing. The herbicide penetrated mainly along leaf veins and the time for complete penetration over the whole leaf was approximately 100 minutes after herbicide spraying. When the coverage of herbicide droplets on the surface of leaves increased, the speed of herbicide penetration also increased. This study suggested a way of characerizing herbicide spatial penetration and distribution in leaves.

• Analytical Science and Technology
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• v.21 no.6
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• pp.553-561
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• 2008

$CNT/TiO_2$ composites were prepared by using multiwall carbon nanotubes (MWCNT) and various titanium alkoxide precursors. The composites were comprehensively characterized by scanning electron microscopy (SEM), field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX) and UV-vis absorption spectroscopy. The photoactivity of the prepared materials under UV irradiation, was tested using the conversion of MB from model aqueous solution. Finally, according to the results of methylene blue (MB) removal experiment, we could see that sample CTOS have better MB removal effect than samples CTIP and CTPP.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.50-50
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• 2008

ZnO has been extensively studied for optoelectronic applications such as blue and ultraviolet (UV) light emitters and detectors, because it has a wide band gap (3.37 eV) anda large exciton binding energy of ~60 meV over GaN (~26 meV). However, the fabrication of the light emitting devices using ZnO homojunctions is suffered from the lack of reproducibility of the p-type ZnO with high hall concentration and mobility. Thus, the ZnO-based p-n heterojunction light emitting diode (LED) using p-Si and p-GaN would be expected to exhibit stable device performance compared to the homojunction LED. The n-ZnO/p-GaN heterostructure is a good candidate for ZnO-based heterojunction LEDs because of their similar physical properties and the reproducibleavailability of p-type GaN. Especially, the reduced lattice mismatch (~1.8 %) and similar crystal structure result in the advantage of acquiring high performance LED devices with low defect density. However, the electroluminescence (EL) of the device using n-ZnO/p-GaN heterojunctions shows the blue and greenish emissions, which are attributed to the emission from the p-GaN and deep-level defects. In this work, the n-ZnO:Ga/p-GaN:Mg heterojunction light emitting diodes (LEDs) were fabricated at different growth temperatures and carrier concentrations in the n-type region. The effects of the growth temperature and carrier concentration on the electrical and emission properties were investigated. The I-V and the EL results showed that the device performance of the heterostructure LEDs, such as turn-on voltage and true ultraviolet emission, developed through the insertion of a thin intrinsic layer between n-ZnO:Ga and p-GaN:Mg. This observation was attributed to a lowering of the energy barriers for the supply of electrons and holes into intrinsic ZnO, and recombination in the intrinsic ZnO with the absence of deep level emission.